Rebecca Williams said: "I was really shocked when I saw the label saying it was degrading sweatshop conditions."

"I used to to shop a lot at Primark but not so much now. The label has made me think about how my clothes are made.""I have no idea who made the label or how it got there - but it does make you think."

Primark says it is investigating the origin of extra labels, and any issues raised. Credit: PA

Primark has faced criticism over its ethics, after a factory collapsed last year in Bangladesh, with more than 1,000 workers killed.

Hundreds worked for a Primark supplier, and the high street chain has pledged to pay compensation to injured workers and the families of those killed.

It insisted it has "a code of conduct in place, to ensure products are made in good working conditions and all employees are treated fairly."

Asked about labels being found in these garments from a Swansea store, a spokesperson for Primark said: "We are investigating the origins of an additional label which has been found in one of our dresses and whether there are issues which need to be looked into."